This paper searches out the reasons why a war is declared and waged. In order to access the necessary information, the head researcher and the students resorted to documentary sources. In this research, three methods were used: the descriptive one, the historical one, and the analytic-deductive one. The research team�s main conclusions are: 1). War did not precede the State, it is a recent scourge; 2). War is basically a product of cultural evolution; 3). The warriors� psychological traits always hide behind the material causes of war.